CRACKING IN RECENT ALLUVIAL SOILS AS RELATED TO EASILY DETERMINED SOIL PROPERTIES

Cracking was studied in fifty soils located in two recent alluvial pla ins and it was related to soil parameters such as clay content, soil m oisture content, bulk density and coefficient of linear extensibility (COLE). The total crack area per unit soil surface, the crack width an d crack depth were measured by tracing them on transparent sheets. The rate of crack development was also studied in a soil immediately afte r irrigation. Results showed that crack width increased initially almo st linearly with decreasing soil moisture content to a certain level a nd then increased in a declining rate until a maximum width was attain ed. Cracks appeared on the soil surface after water was removed from t he large soil pores. The total crack area occupied a significant porti on of the soil surface reaching a maximum value of 22.7%. Measurements of water flow into the cracks during irrigation were significant and in some soils exceeded the conductivity of the uncracked soil surface. An empirical relation was found, which calculates the total crack are a per unit soil surface as a function of clay content, COLE and volume tric moisture content. The average crack width was linearly related to the total crack area measured on the soil surface. Furthermore, the c rack depth in the plow layer was logarithmically related to clay conte nt, COLE and moisture content.